(a) Field of the Invention
This application relates to a system for transporting cryogenic and then superheating the cryogenic fluids at an oil or gas well site or facility. More specifically, but not by way of limitation, to a self-contained tractor and cryogenic fluid vaporization and pressurization system that cooperates with standard tanker trailers for hauling a standard tanker trailer to a well site and provide fracturing fluids for use in fracturing, well servicing, and nitrogen purging.
(b) Discussion of Known Art
The preparation of fracturing fluids is well known. An example of fracturing fluid formulation is provided in U.S. Pat. No. 5,551,516, to Norman et al., which is incorporated herein by reference in its entirety. Although other fluids may be used, a common important component of fracturing fluids is nitrogen, which is used gaseous form to create a foamed fracturing fluid. The foaming of the fracturing fluid provides beneficial mechanical properties to the fracturing fluid, and commonly used gasses to create a foamed fracturing fluid include as air, nitrogen or carbon dioxide. Air, nitrogen or carbon dioxide can each be used by itself as the fracturing fluid, but these gasses are typically combined with other fluids, such as water, in liquid a state, and proppants, to create fracturing foam or fluid (collectively referred to from here forward as simply a “fracturing fluid”. The fracturing fluid is pressurized and delivered through a steel casing that has been inserted in a well bore to a desired location in the well bore. The fracturing fluid is delivered to the desired location at high pressures of 10,000 PSI or greater in order to fracture underground formations in order to create flow passages for any valuable oil or gas deposits that may be found near the well bore.
Since well bores, and their associated casing can extend miles from the drilling rig, the amount of fracturing fluid that must be delivered into the ground to fracture the underlying geological formations can be very large. Thus, the amount of gas used for foaming fracturing fluid also correspondingly large. Accordingly, it is advantageous to haul at one time as much of the substance or compound that is to be used to create the gas for foaming.
As discussed above, nitrogen is commonly used as the gas for foaming the fracturing fluid. A benefit of nitrogen is its abundance and low cost, due to the fact that nitrogen is a major component of air. However, nitrogen must first be separated from other components of air and then be cooled to temperatures that cause nitrogen to enter a liquid state. The cooling of the nitrogen to a liquid state is needed due to the large amount of nitrogen used for the fracturing fluids at the well site. It is well known that transportation of these large amounts of nitrogen is most economically accomplished by transporting the nitrogen in a liquid state.
The equipment and facilities needed for separating and liquefying nitrogen, or other fluids that are to be later expanded in the field to serve as components of fracturing fluids, are large and expensive. Thus these facilities are built as permanent or semi-permanent, centralized, facilities that serve as the hubs for preparation of these fluids. The fluids must then be transported from these facilities to the well site, where they are then heated into a gas, which is then used as a component of the fracturing fluid.
The liquefaction of nitrogen requires that the nitrogen be cooled to what is commonly considered cryogenic temperatures. However, to be useful as a component of fracturing fluid, the liquid nitrogen must be re-heated to a superheated state where the nitrogen is in a gaseous state. Nitrogen must be in a superheated state before it can be used as a gaseous component of fracturing fluid. Typically, this requires heating the liquid nitrogen from about −320° F. (−196° C.) to about 70° F. (+/−20° F., 7° C.). Additionally, since the nitrogen gas must be continuously delivered in appropriate amounts to the fracturing fluid as it is delivered into the well bore; it is essential that the system being used to superheat the nitrogen be capable of transferring great amounts of heat energy to the nitrogen as it is being warmed from cryogenic state to what is essentially room temperature.
The problem of heating the nitrogen is complicated by the fact that nitrogen transitions into a gaseous phase at about −320° F. (−196° C.), and the heat transfer coefficient of nitrogen is reduced dramatically once it enters a gaseous phase. Accordingly, raising the temperature of nitrogen gas requires significantly more heat-transfer surface area and time. Because of this reduced efficiency in the superheating of nitrogen, known systems for gasification of nitrogen are typically quite large. Importantly, the size of known systems require a dedicated truck or skid, which means that fracturing operations require vehicles that are dedicated for transporting the nitrogen itself and separate vehicles/systems for heating the nitrogen to a state and temperature that allows the nitrogen to be useful as a component of fracturing fluid.
Examples of known systems for heating nitrogen for the purpose of using the nitrogen as a component of fracturing fluid include U.S. Pat. No. 4,738,115 to Goode, incorporated herein by reference, and U.S. Pat. No. 4,458,633 to Loesch, also incorporated herein by reference. U.S. Pat. No. 4,599,868 to Lutjens et al., also incorporated herein by reference. Additionally, it is known that coolant from a vehicle can be used for heating a fluid that is to be delivered to a well bore. For example, U.S. Pat. No. 5,656,136 to Gayaut et al., incorporated herein by reference, discloses that engine coolant can be used to heat a fluid that is to be delivered to an oil well bore. However, the Gayaut et al. device suffers from the limitation that it carries the fluid to be heated in reservoir tanks that are a permanent component of the vehicle-mounted system. Thus, the system service time is limited by the capacity of the system's reservoir tanks.
Other systems, such as the system disclosed in U.S. Patent Application Publication No. 2014/0048268 to Chandler, disclose the use of an oil-fired heater that is mounted on a trailer that also includes a heat exchanger system for heating an inert gas that will then be used for fracturing. The Chandler device is mounted on a trailer that is dedicated to the heating system. Thus, the heating system must be hauled to a well site using a semi-tractor or other tow vehicle, and then left at a specific location, next to the well. An important limitation of this type of system is that a semi-tractor must be sent to the drilling site to pick up and move the system to a new location. This results in an inefficient use of equipment, due to the fact that a semi-tractor must be separately dispatched to well site every time the system needs to be moved. Additionally, since the Chandler device does not have its own reservoir of inert gas/fluid, a separate tanker trailer must also be left at the drill site.
Accordingly, a review of known devices reveals that there remains a need for an efficient system that serves to superheat gases for fracturing, such as nitrogen gas, carbon dioxide, or other known fluids or gases used as components of fracturing fluids. More particularly, there remains a need for a heating system that obviates the need to have a semi-tractor for towing the fracturing fluid to the drill site and another semi-tractor for towing the heating and gas pressurization system used for providing superheated gas to fracturing fluid.
Still further, there remains a need for a fracturing gas heating and pressurization system that can be installed on a semi-tractor, which can then be used to haul a standard sized tanker trailer.
There remains a need for a fracturing gas heating and pressurization system that can haul a standard sized tanker trailer and use the fluid from the standard sized tanker trailer to create high-pressure, superheated gas that is ready for use as a component of fracturing fluid.
Still further, there remains a need for a fracturing gas heating and pressurization system that can be retrofitted onto a standard semi-tractor, and preferably onto a semi-tractor with a sleeper cab. The use of a semi-tractor with an integral a sleeper cab allows the use of the conversion of the sleeper cab into a “control cabin”, which protects the monitoring equipment and the operator from the elements.